In the loans table, days is how many days a book was out; for books not back yet, days is empty (NULL). Work out the average of days (leaving the empty ones out), rounded to 1 decimal place with ROUND(…, 1).
The tables
books
id
title
author
genre
pages
year
1
The Night Garden
Mia Lane
story
210
2015
2
Stars for Kids
Tom Hart
science
96
2020
3
Lost at Sea
Mia Lane
story
340
2011
4
Easy Bread
Rosa Bell
food
128
2019
5
The Bug Book
Tom Hart
science
64
2022
6
Soup Days
Rosa Bell
food
150
2008
7
The Red Kite
Ann Cole
story
180
2021
8
Rocks and Rivers
Ann Cole
science
220
2017
8 rows
loans
id
book_id
reader
days
1
1
Leo
14
2
2
Nora
7
3
1
Sam
NULL
4
4
Leo
21
5
5
Nora
NULL
6
3
Ivy
10
7
2
Sam
5
8
7
Ivy
12
8 rows
books
id
title
author
genre
pages
year
1
The Night Garden
Mia Lane
story
210
2015
2
Stars for Kids
Tom Hart
science
96
2020
3
Lost at Sea
Mia Lane
story
340
2011
4
Easy Bread
Rosa Bell
food
128
2019
5
The Bug Book
Tom Hart
science
64
2022
6
Soup Days
Rosa Bell
food
150
2008
7
The Red Kite
Ann Cole
story
180
2021
8
Rocks and Rivers
Ann Cole
science
220
2017
8 rows
loans
id
book_id
reader
days
1
1
Leo
14
2
2
Nora
7
3
1
Sam
NULL
4
4
Leo
21
5
5
Nora
NULL
6
3
Ivy
10
7
2
Sam
5
8
7
Ivy
12
8 rows
query.sql
-- your code here: ROUND(AVG(days), 1) for the average number of days
SELECT days
FROM loans;
Ctrl + Enter runs too
Result
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